lib/isc/symtab.c

/*
 * Copyright (C) 1996-2001, 2004, 2005, 2007, 2011-2013, 2016  Internet Systems Consortium, Inc. ("ISC")
 *
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/.
 */

/* $Id$ */

/*! \file */

#include <config.h>

#include <ctype.h>

#include <isc/magic.h>
#include <isc/mem.h>
#include <isc/string.h>
#include <isc/symtab.h>
#include <isc/util.h>

typedef struct elt {
    char *              key;
    unsigned int            type;
    isc_symvalue_t          value;
    LINK(struct elt)        link;
} elt_t;

typedef LIST(elt_t)         eltlist_t;

#define SYMTAB_MAGIC            ISC_MAGIC('S', 'y', 'm', 'T')
#define VALID_SYMTAB(st)        ISC_MAGIC_VALID(st, SYMTAB_MAGIC)

struct isc_symtab {
    /* Unlocked. */
    unsigned int            magic;
    isc_mem_t *         mctx;
    unsigned int            size;
    unsigned int            count;
    unsigned int            maxload;
    eltlist_t *         table;
    isc_symtabaction_t      undefine_action;
    void *              undefine_arg;
    isc_boolean_t           case_sensitive;
};

isc_result_t
isc_symtab_create(isc_mem_t *mctx, unsigned int size,
          isc_symtabaction_t undefine_action,
          void *undefine_arg,
          isc_boolean_t case_sensitive,
          isc_symtab_t **symtabp)
{
    isc_symtab_t *symtab;
    unsigned int i;

    REQUIRE(mctx != NULL);
    REQUIRE(symtabp != NULL && *symtabp == NULL);
    REQUIRE(size > 0);  /* Should be prime. */

    symtab = (isc_symtab_t *)isc_mem_get(mctx, sizeof(*symtab));
    if (symtab == NULL)
        return (ISC_R_NOMEMORY);

    symtab->mctx = NULL;
    isc_mem_attach(mctx, &symtab->mctx);
    symtab->table = (eltlist_t *)isc_mem_get(mctx,
                         size * sizeof(eltlist_t));
    if (symtab->table == NULL) {
        isc_mem_putanddetach(&symtab->mctx, symtab, sizeof(*symtab));
        return (ISC_R_NOMEMORY);
    }
    for (i = 0; i < size; i++)
        INIT_LIST(symtab->table[i]);
    symtab->size = size;
    symtab->count = 0;
    symtab->maxload = size * 3 / 4;
    symtab->undefine_action = undefine_action;
    symtab->undefine_arg = undefine_arg;
    symtab->case_sensitive = case_sensitive;
    symtab->magic = SYMTAB_MAGIC;

    *symtabp = symtab;

    return (ISC_R_SUCCESS);
}

void
isc_symtab_destroy(isc_symtab_t **symtabp) {
    isc_symtab_t *symtab;
    unsigned int i;
    elt_t *elt, *nelt;

    REQUIRE(symtabp != NULL);
    symtab = *symtabp;
    REQUIRE(VALID_SYMTAB(symtab));

    for (i = 0; i < symtab->size; i++) {
        for (elt = HEAD(symtab->table[i]); elt != NULL; elt = nelt) {
            nelt = NEXT(elt, link);
            if (symtab->undefine_action != NULL)
                   (symtab->undefine_action)(elt->key,
                             elt->type,
                             elt->value,
                             symtab->undefine_arg);
            isc_mem_put(symtab->mctx, elt, sizeof(*elt));
        }
    }
    isc_mem_put(symtab->mctx, symtab->table,
            symtab->size * sizeof(eltlist_t));
    symtab->magic = 0;
    isc_mem_putanddetach(&symtab->mctx, symtab, sizeof(*symtab));

    *symtabp = NULL;
}

static inline unsigned int
hash(const char *key, isc_boolean_t case_sensitive) {
    const char *s;
    unsigned int h = 0;
    int c;

    /*
     * This hash function is similar to the one Ousterhout
     * uses in Tcl.
     */

    if (case_sensitive) {
        for (s = key; *s != '\0'; s++) {
            h += (h << 3) + *s;
        }
    } else {
        for (s = key; *s != '\0'; s++) {
            c = *s;
            c = tolower((unsigned char)c);
            h += (h << 3) + c;
        }
    }

    return (h);
}

#define FIND(s, k, t, b, e) \
    b = hash((k), (s)->case_sensitive) % (s)->size; \
    if ((s)->case_sensitive) { \
        for (e = HEAD((s)->table[b]); e != NULL; e = NEXT(e, link)) { \
            if (((t) == 0 || e->type == (t)) && \
                strcmp(e->key, (k)) == 0) \
                break; \
        } \
    } else { \
        for (e = HEAD((s)->table[b]); e != NULL; e = NEXT(e, link)) { \
            if (((t) == 0 || e->type == (t)) && \
                strcasecmp(e->key, (k)) == 0) \
                break; \
        } \
    }

isc_result_t
isc_symtab_lookup(isc_symtab_t *symtab, const char *key, unsigned int type,
          isc_symvalue_t *value)
{
    unsigned int bucket;
    elt_t *elt;

    REQUIRE(VALID_SYMTAB(symtab));
    REQUIRE(key != NULL);

    FIND(symtab, key, type, bucket, elt);

    if (elt == NULL)
        return (ISC_R_NOTFOUND);

    if (value != NULL)
        *value = elt->value;

    return (ISC_R_SUCCESS);
}

static void
grow_table(isc_symtab_t *symtab) {
    eltlist_t *newtable;
    unsigned int i, newsize, newmax;

    REQUIRE(symtab != NULL);

    newsize = symtab->size * 2;
    newmax = newsize * 3 / 4;
    INSIST(newsize > 0U && newmax > 0U);

    newtable = isc_mem_get(symtab->mctx, newsize * sizeof(eltlist_t));
    if (newtable == NULL)
        return;

    for (i = 0; i < newsize; i++)
        INIT_LIST(newtable[i]);

    for (i = 0; i < symtab->size; i++) {
        elt_t *elt, *nelt;

        for (elt = HEAD(symtab->table[i]); elt != NULL; elt = nelt) {
            unsigned int hv;

            nelt = NEXT(elt, link);

            UNLINK(symtab->table[i], elt, link);
            hv = hash(elt->key, symtab->case_sensitive);
            APPEND(newtable[hv % newsize], elt, link);
        }
    }

    isc_mem_put(symtab->mctx, symtab->table,
            symtab->size * sizeof(eltlist_t));

    symtab->table = newtable;
    symtab->size = newsize;
    symtab->maxload = newmax;
}

isc_result_t
isc_symtab_define(isc_symtab_t *symtab, const char *key, unsigned int type,
          isc_symvalue_t value, isc_symexists_t exists_policy)
{
    unsigned int bucket;
    elt_t *elt;

    REQUIRE(VALID_SYMTAB(symtab));
    REQUIRE(key != NULL);
    REQUIRE(type != 0);

    FIND(symtab, key, type, bucket, elt);

    if (exists_policy != isc_symexists_add && elt != NULL) {
        if (exists_policy == isc_symexists_reject)
            return (ISC_R_EXISTS);
        INSIST(exists_policy == isc_symexists_replace);
        UNLINK(symtab->table[bucket], elt, link);
        if (symtab->undefine_action != NULL)
            (symtab->undefine_action)(elt->key, elt->type,
                          elt->value,
                          symtab->undefine_arg);
    } else {
        elt = (elt_t *)isc_mem_get(symtab->mctx, sizeof(*elt));
        if (elt == NULL)
            return (ISC_R_NOMEMORY);
        ISC_LINK_INIT(elt, link);
        symtab->count++;
    }

    /*
     * Though the "key" can be const coming in, it is not stored as const
     * so that the calling program can easily have writable access to
     * it in its undefine_action function.  In the event that it *was*
     * truly const coming in and then the caller modified it anyway ...
     * well, don't do that!
     */
    DE_CONST(key, elt->key);
    elt->type = type;
    elt->value = value;

    /*
     * We prepend so that the most recent definition will be found.
     */
    PREPEND(symtab->table[bucket], elt, link);

    if (symtab->count > symtab->maxload)
        grow_table(symtab);

    return (ISC_R_SUCCESS);
}

isc_result_t
isc_symtab_undefine(isc_symtab_t *symtab, const char *key, unsigned int type) {
    unsigned int bucket;
    elt_t *elt;

    REQUIRE(VALID_SYMTAB(symtab));
    REQUIRE(key != NULL);

    FIND(symtab, key, type, bucket, elt);

    if (elt == NULL)
        return (ISC_R_NOTFOUND);

    if (symtab->undefine_action != NULL)
        (symtab->undefine_action)(elt->key, elt->type,
                      elt->value, symtab->undefine_arg);
    UNLINK(symtab->table[bucket], elt, link);
    isc_mem_put(symtab->mctx, elt, sizeof(*elt));
    symtab->count--;

    return (ISC_R_SUCCESS);
}

unsigned int
isc_symtab_count(isc_symtab_t *symtab) {
    REQUIRE(VALID_SYMTAB(symtab));
    return (symtab->count);
}